@misc{SekulicSchaibleMuelleretal.2025, author = {Sekulic, Ivan and Schaible, Jonas and M{\"u}ller, Gabriel and Plock, Matthias and Burger, Sven and Martinez-Lahuerta, Victor J. and Gaaloul, Naceur and Schneider, Philipp-Immanuel}, title = {Data publication for Physics-informed Bayesian optimization of expensive-to-evaluate black-box functions}, journal = {Zenodo}, doi = {10.5281/zenodo.16751507}, year = {2025}, language = {en} } @misc{BetzBinkowskiFischbachetal.2025, author = {Betz, Fridtjof and Binkowski, Felix and Fischbach, Jan David and Feldman, Nick and Zschiedrich, Lin and Rockstuhl, Carsten and Koenderink, A. Femius and Burger, Sven}, title = {Uncovering Hidden Resonances in Non-Hermitian Systems with Scattering Thresholds (Laser Photonics Rev. 19(21)/2025)}, volume = {19}, journal = {Laser Photonics Rev.}, number = {21}, doi = {10.1002/lpor.70534}, pages = {e70534}, year = {2025}, language = {en} } @article{AbouHamdanJanaColometal.2026, author = {Abou Hamdan, Loubnan and Jana, Aloke and Colom, R{\´e}mi and Aboujoussef, Nour and Carlson, Cooper and Overvig, Adam and Binkowski, Felix and Burger, Sven and Genevet, Patrice}, title = {A Complex-Frequency Framework for Kerker Unidirectionality in Photonic Resonators}, doi = {10.21203/rs.3.rs-8444305/v1}, year = {2026}, language = {en} } @article{TrowerDjurdjevacConradKlus2025, author = {Trower, Maia and Djurdjevac Conrad, Natasa and Klus, Stefan}, title = {Clustering Time-Evolving Networks Using the Spatiotemporal Graph Laplacian}, volume = {35}, journal = {Chaos: An Interdisciplinary Journal of Nonlinear Science}, arxiv = {http://arxiv.org/abs/2407.12864}, doi = {10.1063/5.0228419}, pages = {013126}, year = {2025}, abstract = {Time-evolving graphs arise frequently when modeling complex dynamical systems such as social networks, traffic flow, and biological processes. Developing techniques to identify and analyze communities in these time-varying graph structures is an important challenge. In this work, we generalize existing spectral clustering algorithms from static to dynamic graphs using canonical correlation analysis (CCA) to capture the temporal evolution of clusters. Based on this extended canonical correlation framework, we define the spatio-temporal graph Laplacian and investigate its spectral properties. We connect these concepts to dynamical systems theory via transfer operators, and illustrate the advantages of our method on benchmark graphs by comparison with existing methods. We show that the spatio-temporal graph Laplacian allows for a clear interpretation of cluster structure evolution over time for directed and undirected graphs.}, language = {en} } @article{StraubeHoefling2024, author = {Straube, Arthur and H{\"o}fling, Felix}, title = {Memory effects in colloidal motion under confinement and driving}, volume = {57}, journal = {J. Phys. A: Math. Theor.}, publisher = {IOP Publishing}, issn = {1751-8113}, doi = {10.1088/1751-8121/ad5b2d}, pages = {295003}, year = {2024}, abstract = {The transport of individual particles in inhomogeneous environments is complex and exhibits non-Markovian responses. The latter may be quantified by a memory function within the framework of the linear generalised Langevin equation (GLE). Here, we exemplify the implications of steady driving on the memory function of a colloidal model system for Brownian motion in a corrugated potential landscape, specifically, for one-dimensional motion in a sinusoidal potential. To this end, we consider the overdamped limit of the GLE, which is facilitated by separating the memory function into a singular (Markovian) and a regular (non-Markovian) part. Relying on exact solutions for the investigated model, we show that the random force entering the GLE must display a bias far from equilibrium, which corroborates a recent general prediction. Based on data for the mean-square displacement (MSD) obtained from Brownian dynamics simulations, we estimate the memory function for different driving strengths and show that already moderate driving accelerates the decay of the memory function by several orders of magnitude in time. We find that the memory may persist on much longer timescales than expected from the convergence of the MSD to its long-time asymptote. Furthermore, the functional form of the memory function changes from a monotonic decay to a non-monotonic, damped oscillatory behaviour, which can be understood from a competition of confined motion and depinning. Our analysis of the simulation data further reveals a pronounced non-Gaussianity, which questions the Gaussian approximation of the random force entering the GLE.}, language = {en} } @article{BonifaceStraubeTierno2024, author = {Boniface, Dolachai and Straube, Arthur and Tierno, Pietro}, title = {Photocatalytic magnetic microgyroscopes with activity-tunable precessional dynamics}, volume = {24}, journal = {Nano Letters}, number = {47}, arxiv = {http://arxiv.org/abs/2407.11640}, doi = {10.1021/acs.nanolett.4c03386}, pages = {14950 -- 14956}, year = {2024}, abstract = {Magnetic nano/microrotors are passive elements that spin around an axis due to an external rotating field while remaining confined to a close plane. They have been used to date in different applications related to fluid mixing, drug delivery or biomedicine. Here we realize an active version of a magnetic microgyroscope which is simultaneously driven by a photo-activated catalytic reaction and a rotating magnetic field. We investigate the uplift dynamics of this colloidal spinner when it stands up and precesses around its long axis while self-propelling due to the light induced decomposition of hydrogen peroxide in water. By combining experiments with theory, we show that activity emerging from the cooperative action of phoretic and osmotic forces effectively increase the gravitational torque which counteracts the magnetic and viscous ones, and carefully measure its contribution.}, language = {en} } @misc{VillaniWeiser2024, author = {Villani, Paolo and Weiser, Martin}, title = {Adaptive Gaussian process regression for inverse problems. ALGORITMY 2024}, year = {2024}, abstract = {This submission contains the code used for the proceedings paper for ALGORITMY 2024, concerning surrogate model-based inverse problems. Version 2 modified plot appearances and fixed some minor typos.}, language = {en} } @article{ErnstAsselineauTillmannetal.2024, author = {Ernst, Marco and Asselineau, Charles-Alexis and Tillmann, Peter and J{\"a}ger, Klaus and Becker, Christiane}, title = {Modelling bifacial irradiance - Step-by-step comparison and validation of view factor and ray tracing models}, volume = {369}, journal = {Appl. Energy}, publisher = {Elsevier BV}, issn = {0306-2619}, doi = {10.1016/j.apenergy.2024.123574}, pages = {123574}, year = {2024}, language = {en} } @misc{SekulicSchneiderHammerschmidtetal.2024, author = {Sekulic, Ivan and Schneider, Philipp-Immanuel and Hammerschmidt, Martin and Burger, Sven}, title = {Machine-learning driven design of metasurfaces: learn the physics and not the objective function}, volume = {PC13017}, journal = {Proc. SPIE}, doi = {10.1117/12.3022119}, pages = {PC130170X}, year = {2024}, language = {en} } @misc{BoppPlockTuranetal.2024, author = {Bopp, Julian M. and Plock, Matthias and Turan, Tim and Pieplow, Gregor and Burger, Sven and Schr{\"o}der, Tim}, title = {'Sawfish' Photonic Crystal Cavity for Near-Unity Emitter-to-Fiber Interfacing in Quantum Network Applications (Advanced Optical Materials 13/2024)}, volume = {12}, journal = {Adv. Optical Mater.}, doi = {10.1002/adom.202470046}, pages = {2470046}, year = {2024}, language = {en} } @article{KlusDjurdjevacConrad2024, author = {Klus, Stefan and Djurdjevac Conrad, Natasa}, title = {Dynamical systems and complex networks: A Koopman operator perspective}, volume = {5}, journal = {Journal of Physics: Complexity}, number = {4}, publisher = {IOP Publishing}, arxiv = {http://arxiv.org/abs/2405.08940}, doi = {10.1088/2632-072X/ad9e60}, pages = {041001}, year = {2024}, abstract = {The Koopman operator has entered and transformed many research areas over the last years. Although the underlying concept-representing highly nonlinear dynamical systems by infinite-dimensional linear operators-has been known for a long time, the availability of large data sets and efficient machine learning algorithms for estimating the Koopman operator from data make this framework extremely powerful and popular. Koopman operator theory allows us to gain insights into the characteristic global properties of a system without requiring detailed mathematical models. We will show how these methods can also be used to analyze complex networks and highlight relationships between Koopman operators and graph Laplacians.}, language = {en} } @article{KruegerManleyBergmannetal.2024, author = {Kr{\"u}ger, Jan and Manley, Phillip and Bergmann, Detlef and K{\"o}ning, Rainer and Bodermann, Bernd and Eder, Christian and Heinrich, Andreas and Schneider, Philipp-Immanuel and Hammerschmidt, Martin and Zschiedrich, Lin and Manske, Eberhard}, title = {Introduction and application of a new approach for model-based optical bidirectional measurements}, volume = {35}, journal = {Meas. Sci. Technol.}, doi = {10.1088/1361-6501/ad4b53}, pages = {085014}, year = {2024}, language = {en} } @article{ManleyHammerschmidtZschiedrichetal.2024, author = {Manley, Phillip and Hammerschmidt, Martin and Zschiedrich, Lin and J{\"a}ger, Klaus and Becker, Christiane and Burger, Sven}, title = {Modelling luminescent coupling in multi-junction solar cells: perovskite silicon tandem case study}, volume = {13014}, journal = {Proc. SPIE}, arxiv = {http://arxiv.org/abs/2409.15987}, doi = {10.1117/12.3023941}, pages = {1301404}, year = {2024}, language = {en} } @inproceedings{SchaibleYooWinartoetal.2024, author = {Schaible, Jonas and Yoo, Danbi and Winarto, Hanifa and Miaskiewicz, Alexandra and Albrecht, Steve and Wessels, Andreas and Bl{\"a}si, Benedikt and Burger, Sven and Jaeger, Klaus and Becker, Christiane}, title = {On aesthetical appearance of colored perovskite solar modules}, volume = {PC13014}, booktitle = {Proc. SPIE}, publisher = {SPIE}, doi = {10.1117/12.3017427}, pages = {PC1301406}, year = {2024}, language = {en} } @inproceedings{BeckerBlaesiBurgeretal.2024, author = {Becker, Christiane and Bl{\"a}si, Benedikt and Burger, Sven and Ehrler, Bruno and Gordon, Ivan and Isabella, Olindo and J{\"a}ger, Klaus and Jost, Marko and Manley, Phillip and Mu{\~n}oz, Delfina and Paetzold, Ulrich W. and Sai, Hitoshi and Yablonovitch, Eli}, title = {Optical challenges for terawatt-scale photovoltaics}, volume = {PC13014}, booktitle = {Proc. SPIE}, publisher = {SPIE}, doi = {10.1117/12.3016415}, pages = {PC1301401}, year = {2024}, language = {en} } @inproceedings{SemlerWeiser2025, author = {Semler, Phillip and Weiser, Martin}, title = {Adaptive gradient-enhanced Gaussian process surrogates for inverse problems}, booktitle = {Mathematical Optimization for Machine Learning: Proceedings of the MATH+ Thematic Einstein Semester 2023}, editor = {Fackeldey, Konstantin and Kannan, Aswin and Pokutta, Sebastian and Sharma, Kartikey and Walter, Daniel and Walther, Andrea and Weiser, Martin}, publisher = {De Gruyter}, arxiv = {http://arxiv.org/abs/2404.01864}, doi = {10.1515/9783111376776-005}, pages = {59 -- 78}, year = {2025}, abstract = {Generating simulated training data needed for constructing sufficiently accurate surrogate models to be used for efficient optimization or parameter identification can incur a huge computational effort in the offline phase. We consider a fully adaptive greedy approach to the computational design of experiments problem using gradient-enhanced Gaussian process regression as surrogates. Designs are incrementally defined by solving an optimization problem for accuracy given a certain computational budget. We address not only the choice of evaluation points but also of required simulation accuracy, both of values and gradients of the forward model. Numerical results show a significant reduction of the computational effort compared to just position-adaptive and static designs as well as a clear benefit of including gradient information into the surrogate training.}, language = {en} } @article{DjurdjevacConradQuangVuNagel2024, author = {Djurdjevac Conrad, Natasa and Quang Vu, Nhu and Nagel, Soeren}, title = {Co-evolving networks for opinion and social dynamics in agent-based models}, volume = {34}, journal = {Chaos: An Interdisciplinary Journal of Nonlinear Science}, number = {9}, issn = {1054-1500}, arxiv = {http://arxiv.org/abs/2407.00145}, doi = {10.1063/5.0226054}, year = {2024}, abstract = {The rise of digital social media has strengthened the coevolution of public opinions and social interactions, that shape social structures and collective outcomes in increasingly complex ways. Existing literature often explores this interplay as a one-directional influence, focusing on how opinions determine social ties within adaptive networks. However, this perspective overlooks the intrinsic dynamics driving social interactions, which can significantly influence how opinions form and evolve. In this work, we address this gap, by introducing the co-evolving opinion and social dynamics using stochastic agent-based models. Agents' mobility in a social space is governed by both their social and opinion similarity with others. Similarly, the dynamics of opinion formation is driven by the opinions of agents in their social vicinity. We analyze the underlying social and opinion interaction networks and explore the mechanisms influencing the appearance of emerging phenomena, like echo chambers and opinion consensus. To illustrate the model's potential for real-world analysis, we apply it to General Social Survey data on political identity and public opinion regarding governmental issues. Our findings highlight the model's strength in capturing the coevolution of social connections and individual opinions over time.}, language = {en} } @misc{KuenLoefflerTsarapkinetal.2024, author = {Kuen, Lilli and L{\"o}ffler, Lorenz and Tsarapkin, Aleksei and Zschiedrich, Lin and Feichtner, Thorsten and Burger, Sven and H{\"o}flich, Katja}, title = {Source Code and Simulation Results: Chiral and directional optical emission from a dipole source coupled to a helical plasmonic antenna}, journal = {Zenodo}, doi = {10.5281/zenodo.10598255}, pages = {doi: 10.5281/zenodo.10598255}, year = {2024}, language = {en} } @article{MuellerMartinezLahuertaSekulicetal.2025, author = {M{\"u}ller, Gabriel and Mart{\´i}nez-Lahuerta, Victor J. and Sekulic, Ivan and Burger, Sven and Schneider, Philipp-Immanuel and Gaaloul, Naceur}, title = {Bayesian optimization for state engineering of quantum gases}, volume = {10}, journal = {Quantum Sci. Technol.}, arxiv = {http://arxiv.org/abs/2404.18234}, doi = {10.1088/2058-9565/ad9050}, pages = {015033}, year = {2025}, language = {en} } @article{ErbanWinkelmann2025, author = {Erban, Radek and Winkelmann, Stefanie}, title = {Multi-grid reaction-diffusion master equation: applications to morphogen gradient modelling}, volume = {87}, journal = {Bulletin of Mathematical Biology}, arxiv = {http://arxiv.org/abs/arXiv:2405.02117}, doi = {10.1007/s11538-024-01377-y}, pages = {6}, year = {2025}, abstract = {The multi-grid reaction-diffusion master equation (mgRDME) provides a generalization of stochastic compartment-based reaction-diffusion modelling described by the standard reaction-diffusion master equation (RDME). By enabling different resolutions on lattices for biochemical species with different diffusion constants, the mgRDME approach improves both accuracy and efficiency of compartment-based reaction-diffusion simulations. The mgRDME framework is examined through its application to morphogen gradient formation in stochastic reaction-diffusion scenarios, using both an analytically tractable first-order reaction network and a model with a second-order reaction. The results obtained by the mgRDME modelling are compared with the standard RDME model and with the (more detailed) particle-based Brownian dynamics simulations. The dependence of error and numerical cost on the compartment sizes is defined and investigated through a multi-objective optimization problem.}, language = {en} } @inproceedings{VillaniUngerWeiser2024, author = {Villani, Paolo and Unger, J{\"o}rg F. and Weiser, Martin}, title = {Adaptive Gaussian Process Regression for Bayesian inverse problems}, booktitle = {Proceedings of the Conference Algoritmy 2024}, pages = {214 -- 224}, year = {2024}, abstract = {We introduce a novel adaptive Gaussian Process Regression (GPR) methodology for efficient construction of surrogate models for Bayesian inverse problems with expensive forward model evaluations. An adaptive design strategy focuses on optimizing both the positioning and simulation accuracy of training data in order to reduce the computational cost of simulating training data without compromising the fidelity of the posterior distributions of parameters. The method interleaves a goal-oriented active learning algorithm selecting evaluation points and tolerances based on the expected impact on the Kullback-Leibler divergence of surrogated and true posterior with a Markov Chain Monte Carlo sampling of the posterior. The performance benefit of the adaptive approach is demonstrated for two simple test problems.}, language = {en} } @article{AndresArconesWeiserKoutsourelakisetal.2023, author = {Andr{\´e}s Arcones, Daniel and Weiser, Martin and Koutsourelakis, Faidon-Stelios and Unger, J{\"o}rg F.}, title = {A Bayesian Framework for Simulation-based Digital Twins of Bridges}, volume = {6}, journal = {EUROSTRUCT 2023:European Association on Quality Control of Bridges and Structures: Digital Transformation in Sustainability}, number = {5}, doi = {10.1002/cepa.2177}, pages = {734 -- 740}, year = {2023}, abstract = {Simulation-based digital twins have emerged as a powerful tool for evaluating the mechanical response of bridges. As virtual representations of physical systems, digital twins can provide a wealth of information that complements traditional inspection and monitoring data. By incorporating virtual sensors and predictive maintenance strategies, they have the potential to improve our understanding of the behavior and performance of bridges over time. However, as bridges age and undergo regular loading and extreme events, their structural characteristics change, often differing from the predictions of their initial design. Digital twins must be continuously adapted to reflect these changes. In this article, we present a Bayesian framework for updating simulation-based digital twins in the context of bridges. Our approach integrates information from measurements to account for inaccuracies in the simulation model and quantify uncertainties. Through its implementation and assessment, this work demonstrates the potential for digital twins to provide a reliable and up-to-date representation of bridge behavior, helping to inform decision-making for maintenance and management.}, language = {en} } @inproceedings{AndresArconesWeiserKoutsourelakisetal.2023, author = {Andr{\´e}s Arcones, Daniel and Weiser, Martin and Koutsourelakis, Faidon-Stelios and Unger, J{\"o}rg F.}, title = {Evaluation of Model Bias Identification Approaches Based on Bayesian Inference and Applications to Digital Twins}, booktitle = {5th ECCOMAS Thematic Conference on Uncertainty Quantification in Computational Sciences and Engineering}, pages = {1 -- 15}, year = {2023}, abstract = {In recent years, the use of simulation-based digital twins for monitoring and assessment of complex mechanical systems has greatly expanded. Their potential to increase the information obtained from limited data makes them an invaluable tool for a broad range of real-world applications. Nonetheless, there usually exists a discrepancy between the predicted response and the measurements of the system once built. One of the main contributors to this difference in addition to miscalibrated model parameters is the model error. Quantifying this socalled model bias (as well as proper values for the model parameters) is critical for the reliable performance of digital twins. Model bias identification is ultimately an inverse problem where information from measurements is used to update the original model. Bayesian formulations can tackle this task. Including the model bias as a parameter to be inferred enables the use of a Bayesian framework to obtain a probability distribution that represents the uncertainty between the measurements and the model. Simultaneously, this procedure can be combined with a classic parameter updating scheme to account for the trainable parameters in the original model. This study evaluates the effectiveness of different model bias identification approaches based on Bayesian inference methods. This includes more classical approaches such as direct parameter estimation using MCMC in a Bayesian setup, as well as more recent proposals such as stat-FEM or orthogonal Gaussian Processes. Their potential use in digital twins, generalization capabilities, and computational cost is extensively analyzed.}, language = {en} } @article{MaierWeiserConrad2025, author = {Maier, Kristina and Weiser, Martin and Conrad, Tim}, title = {Hybrid PDE-ODE Models for Efficient Simulation of Infection Spread in Epidemiology}, volume = {481}, journal = {Proceedings of the Royal Society A}, number = {2306}, publisher = {Royal Society}, arxiv = {http://arxiv.org/abs/2405.12938}, doi = {10.1098/rspa.2024.0421}, year = {2025}, abstract = {This paper introduces a novel hybrid model combining Partial Differential Equations (PDEs) and Ordinary Differential Equations (ODEs) to simulate infectious disease dynamics across geographic regions. By leveraging the spatial detail of PDEs and the computational efficiency of ODEs, the model enables rapid evaluation of public health interventions. Applied to synthetic environments and real-world scenarios in Lombardy, Italy, and Berlin, Germany, the model highlights how interactions between PDE and ODE regions affect infection dynamics, especially in high-density areas. Key findings reveal that the placement of model boundaries in densely populated regions can lead to inaccuracies in infection spread, suggesting that boundaries should be positioned in areas of lower population density to better reflect transmission dynamics. Additionally, regions with low population density hinder infection flow, indicating a need for incorporating, e.g., jumps in the model to enhance its predictive capabilities. Results indicate that the hybrid model achieves a balance between computational speed and accuracy, making it a valuable tool for policymakers in real-time decision-making and scenario analysis in epidemiology and potentially in other fields requiring similar modeling approaches.}, language = {en} } @article{AndresArconesWeiserKoutsourelakisetal.2024, author = {Andr{\´e}s Arcones, Daniel and Weiser, Martin and Koutsourelakis, Faidon-Stelios and Unger, J{\"o}rg F.}, title = {Model bias identification for Bayesian calibration of stochastic digital twins of bridges}, volume = {41}, journal = {Applied Stochastic Models in Business and Industry}, number = {3}, doi = {10.1002/asmb.2897}, year = {2024}, abstract = {Simulation-based digital twins must provide accurate, robust and reliable digital representations of their physical counterparts. Quantifying the uncertainty in their predictions plays, therefore, a key role in making better-informed decisions that impact the actual system. The update of the simulation model based on data must be then carefully implemented. When applied to complex standing structures such as bridges, discrepancies between the computational model and the real system appear as model bias, which hinders the trustworthiness of the digital twin and increases its uncertainty. Classical Bayesian updating approaches aiming to infer the model parameters often fail at compensating for such model bias, leading to overconfident and unreliable predictions. In this paper, two alternative model bias identification approaches are evaluated in the context of their applicability to digital twins of bridges. A modularized version of Kennedy and O'Hagan's approach and another one based on Orthogonal Gaussian Processes are compared with the classical Bayesian inference framework in a set of representative benchmarks. Additionally, two novel extensions are proposed for such models: the inclusion of noise-aware kernels and the introduction of additional variables not present in the computational model through the bias term. The integration of such approaches in the digital twin corrects the predictions, quantifies their uncertainty, estimates noise from unknown physical sources of error and provides further insight into the system by including additional pre-existing information without modifying the computational model.}, language = {en} } @article{WehlitzSadeghiMontefuscoetal.2025, author = {Wehlitz, Nathalie and Sadeghi, Mohsen and Montefusco, Alberto and Sch{\"u}tte, Christof and Pavliotis, Grigorios A. and Winkelmann, Stefanie}, title = {Approximating particle-based clustering dynamics by stochastic PDEs}, volume = {24}, journal = {SIAM Journal on Applied Dynamical Systems}, number = {2}, arxiv = {http://arxiv.org/abs/2407.18952}, doi = {10.1137/24M1676661}, pages = {1231 -- 1250}, year = {2025}, abstract = {This work proposes stochastic partial differential equations (SPDEs) as a practical tool to replicate clustering effects of more detailed particle-based dynamics. Inspired by membrane mediated receptor dynamics on cell surfaces, we formulate a stochastic particle-based model for diffusion and pairwise interaction of particles, leading to intriguing clustering phenomena. Employing numerical simulation and cluster detection methods, we explore the approximation of the particle-based clustering dynamics through mean-field approaches. We find that SPDEs successfully reproduce spatiotemporal clustering dynamics, not only in the initial cluster formation period, but also on longer time scales where the successive merging of clusters cannot be tracked by deterministic mean-field models. The computational efficiency of the SPDE approach allows us to generate extensive statistical data for parameter estimation in a simpler model that uses a Markov jump process to capture the temporal evolution of the cluster number.}, language = {en} } @article{HoeflingStraube2025, author = {H{\"o}fling, Felix and Straube, Arthur}, title = {Langevin equations and a geometric integration scheme for the overdamped limit of rotational Brownian motion of axisymmetric particles}, volume = {7}, journal = {Physical Review Research}, arxiv = {http://arxiv.org/abs/2403.04501}, doi = {10.1103/wzdn-29p4}, pages = {043034}, year = {2025}, abstract = {The translational motion of anisotropic or self-propelled colloidal particles is closely linked with the particle's orientation and its rotational Brownian motion. In the overdamped limit, the stochastic evolution of the orientation vector follows a diffusion process on the unit sphere and is characterized by an orientation-dependent ("multiplicative") noise. As a consequence, the corresponding Langevin equation attains different forms depending on whether Itō's or Stratonovich's stochastic calculus is used. We clarify that both forms are equivalent and derive them in a top-down approach from a geometric construction of Brownian motion on the unit sphere, based on infinitesimal random rotations. Our approach suggests further a geometric integration scheme for rotational Brownian motion, which preserves the normalization constraint of the orientation vector exactly. We show that a simple implementation of the scheme, using Gaussian random rotations, converges weakly at order 1 of the integration time step, and we outline an advanced variant of the scheme that is weakly exact for an arbitrarily large time step. Due to a favorable prefactor of the discretization error, already the Gaussian scheme allows for integration time steps that are one order of magnitude larger compared to a commonly used algorithm for rotational Brownian dynamics simulations based on projection on the constraining manifold. For torques originating from constant external fields, we prove by virtue of the Fokker-Planck equation that the constructed diffusion process satisfies detailed balance and converges to the correct equilibrium distribution. The analysis is restricted to time-homogeneous rotational Brownian motion (i.e., a single rotational diffusion constant), which is relevant for axisymmetric particles and also chemically anisotropic spheres, such as self-propelled Janus particles.}, language = {en} } @article{SchaibleWinartoŠkorjancetal.2025, author = {Schaible, Jonas and Winarto, Hanifah and Škorjanc, Viktor and Yoo, Danbi and Zimmermann, Lea and J{\"a}ger, Klaus and Sekulic, Ivan and Schneider, Philipp-Immanuel and Burger, Sven and Wessels, Andreas and Bl{\"a}si, Benedikt and Becker, Christiane}, title = {Optimizing Aesthetic Appearance of Perovskite Solar Cells Using Color Filters}, volume = {9}, journal = {Solar RRL}, publisher = {Wiley}, doi = {10.1002/solr.202400627}, pages = {2400627}, year = {2025}, abstract = {The significance of color aesthetics in photovoltaic (PV) modules gains importance, especially in design-centric applications like building-integrated PVs. Color filters based on distributed Bragg reflectors, consisting of alternating thin-film layers of different refractive indices, can modify the appearance of standard silicon modules. This approach is also extended to optimize the color appearance of emerging PV technologies such as perovskite solar cells, which typically exhibit a less appealing gray-brownish appearance. In this contribution, perovskite solar-cell stacks combined with MorphoColor color filters are presented. Angular-resolved reflectance simulations based on wave optics and ray tracing with experimental data are validated, and the color appearance from various viewing angles is evaluated. Additionally, the impact of individual layers on color appearance and the maximum achievable short-circuit current density in the perovskite solar cell is investigated. By applying Bayesian optimization, the color distance is minimized to the targeted appearance. Tailoring the bridging layers between the color filter and the perovskite solar cell is found to strongly influence the color impression due to the coherently combined color filter and perovskite solar cell. The presented color optimization concept allows to customize the aesthetics of emerging PV thin-film technologies such as perovskite solar cells.}, language = {en} } @misc{RocheBetzYangetal.2024, author = {Roche, L{\´e}o J. and Betz, Fridtjof and Yang, Yuhui and Limame, Imad and Shih, Ching-Wen and Burger, Sven and Reitzenstein, Stephan}, title = {Inside Front Cover: Numerical Investigation of a Coupled Micropillar - Waveguide System for Integrated Quantum Photonic Circuits (Adv. Quantum Technol. 12/2024)}, volume = {7}, journal = {Adv. Quantum Technol.}, doi = {10.1002/qute.202470036}, pages = {2470036}, year = {2024}, language = {en} } @inproceedings{MukherjeeBurgerSiefkeetal.2024, author = {Mukherjee, Deshabrato and Burger, Sven and Siefke, Thomas and Gour, Jeetendra and Bodermann, Bernd and Petrik, Peter}, title = {Modeling of dimensions and sensing properties of gold gratings by spectroscopic ellipsometry and finite element method}, volume = {309}, booktitle = {EPJ Web of Conferences}, doi = {10.1051/epjconf/202430902016}, pages = {02016}, year = {2024}, language = {en} } @article{DjurdjevacConradTonelloZonkeretal.2025, author = {Djurdjevac Conrad, Natasa and Tonello, Elisa and Zonker, Johannes and Siebert, Heike}, title = {Detection of dynamic communities in temporal networks with sparse data}, volume = {10}, journal = {Applied Network Science}, publisher = {Springer International Publishing}, doi = {10.1007/s41109-024-00687-3}, year = {2025}, abstract = {Temporal networks are a powerful tool for studying the dynamic nature of a wide range of real-world complex systems, including social, biological and physical systems. In particular, detection of dynamic communities within these networks can help identify important cohesive structures and fundamental mechanisms driving systems behaviour. However, when working with real-world systems, available data is often limited and sparse, due to missing data on systems entities, their evolution and interactions, as well as uncertainty regarding temporal resolution. This can hinder accurate representation of the system over time and result in incomplete or biased community dynamics. In this paper, we compare established methods for community detection and, using synthetic data experiments and real-world case studies, we evaluate the impact of data sparsity on the quality of identified dynamic communities. Our results give valuable insights on the evolution of systems with sparse data, which are less studied in existing literature, but are frequently encountered in real-world applications.}, language = {en} } @article{ZimperCornalbaDjurdjevacConradetal.2025, author = {Zimper, Sebastian and Cornalba, Federico and Djurdjevac Conrad, Natasa and Djurdjevac, Ana}, title = {On reduced inertial PDE models for Cucker-Smale flocking dynamics}, volume = {481}, journal = {Proceedings of the Royal Society A}, publisher = {Royal Society}, arxiv = {http://arxiv.org/abs/2407.18717}, doi = {https://doi.org/10.1098/rspa.2024.0675}, year = {2025}, abstract = {In particle systems, flocking refers to the phenomenon where particles' individual velocities eventually align. The Cucker-Smale model is a well-known mathematical framework that describes this behaviour. Many continuous descriptions of the Cucker-Smale model use PDEs with both particle position and velocity as independent variables, thus providing a full description of the particles mean-field limit (MFL) dynamics. In this paper, we introduce a novel reduced inertial PDE model consisting of two equations that depend solely on particle position. In contrast to other reduced models, ours is not derived from the MFL, but directly includes the model reduction at the level of the empirical densities, thus allowing for a straightforward connection to the underlying particle dynamics. We present a thorough analytical investigation of our reduced model, showing that: firstly, our reduced PDE satisfies a natural and interpretable continuous definition of flocking; secondly, in specific cases, we can fully quantify the discrepancy between PDE solution and particle system. Our theoretical results are supported by numerical simulations.}, language = {en} } @article{FischbachBetzAsadovaetal.2025, author = {Fischbach, Jan David and Betz, Fridtjof and Asadova, Nigar and Tassan, Pietro and Urbonas, Darius and St{\"o}ferle, Thilo and Mahrt, Rainer F. and Burger, Sven and Rockstuhl, Carsten and Binkowski, Felix and Sturges, Thomas Jebb}, title = {A framework to compute resonances arising from multiple scattering}, volume = {8}, journal = {Adv. Theory Simul.}, arxiv = {http://arxiv.org/abs/2409.05563}, doi = {10.1002/adts.202400989}, pages = {2400989}, year = {2025}, language = {en} } @article{JaegerTejadaBerwigetal.2025, author = {J{\"a}ger, Klaus and Tejada, Alvarjo and Berwig, Sebastian and Hammerschmidt, Martin and Tockhorn, Philipp and Albrecht, Steve and Becker, Christiane}, title = {Optical Simulations of Nanotextured All-Perovskite Tandem Solar Cells}, volume = {8}, journal = {Adv. Theory Simul.}, doi = {10.1002/adts.202400724}, pages = {2400724}, year = {2025}, language = {en} } @inproceedings{BinkowskiBetzHammerschmidtetal.2024, author = {Binkowski, Felix and Betz, Fridtjof and Hammerschmidt, Martin and Zschiedrich, Lin and Burger, Sven}, title = {Poles and Zeros in Resonant Nano-Photonic Systems}, booktitle = {2024 Conference on Lasers and Electro-Optics Pacific Rim (CLEO-PR)}, doi = {10.1109/CLEO-PR60912.2024.10676837}, year = {2024}, language = {en} } @inproceedings{JaegerBurgerAeberhardetal.2024, author = {J{\"a}ger, Klaus and Burger, Sven and Aeberhard, Urs and Llado, Esther Alarcon and Bl{\"a}si, Benedikt and Ehrler, Bruno and Favre, Wilfried and Fejfar, Anton{\´i}n and Gageot, Tristan and Gordon, Ivan and Helmers, Henning and H{\"o}hn, Oliver and Isabella, Olindo and Jošt, Marko and Ledinsk{\´y}, Martin and Mandal, Jyotirmoy and Manley, Phillip and Munoz, Delfina and Lizcano, Juan Camilo Ortiz and Paetzold, Ulrich W. and Raman, Aaswath P. and Sai, Hitoshi and Saive, Rebecca and Schmid, Martina and Yablonovitch, Eli and Becker, Christiane}, title = {A Roadmap on Optics for Terawatt Scale Photovoltaics}, booktitle = {Advanced Photonics Congress 2024}, publisher = {Optica Publishing Group}, doi = {10.1364/SELED.2024.STu2G.5}, pages = {STu2G.5}, year = {2024}, language = {en} } @article{ArmasMerbisMeylahnetal.2025, author = {Armas, Jay and Merbis, Wout and Meylahn, Janusz M and Rafiee Rad, Soroush and del Razo, Mauricio J}, title = {Risk aversion can promote cooperation}, volume = {6}, journal = {Journal of Physics: Complexity}, number = {1}, arxiv = {http://arxiv.org/abs/2306.05971}, doi = {10.1088/2632-072X/adb234}, year = {2025}, abstract = {Cooperative dynamics are central to our understanding of many phenomena in living and complex systems. However, we lack a universal mechanism to explain the emergence of cooperation. We present a novel framework for modelling social dilemma games with an arbitrary number of players by combining reaction networks, methods from quantum mechanics applied to stochastic complex systems, game theory and stochastic simulations of molecular reactions. Using this framework, we propose a novel and robust mechanism for cooperation based on risk aversion that leads to cooperative behaviour in population games. Rather than individuals seeking to maximise payouts in the long run, individuals seek to obtain a minimum set of resources with a given level of confidence and in a limited time span. We show that this mechanism can lead to the emergence of new equilibria in a range of social dilemma games.}, language = {en} } @article{AsadovaAchouriArjasetal.2025, author = {Asadova, Nigar and Achouri, Karim and Arjas, Kristian and Ajugui{\´e}, Baptiste and Aydin, Roland and Baron, Alexandre and Beutel, Dominik and Bodermann, Bernd and Boussaoud, Kaoutar and Burger, Sven and Choi, Minseok and Czajkowski, Krzysztof and Evlyukhin, Andrey B. and Fazel-Najafabadi, Atefeh and Fernandez-Corbaton, Ivan and Garg, Puneet and Globosits, David and Hohenester, Ulrich and Kim, Hongyoon and Kim, Seokwoo and Lalanne, Philippe and Le Ru, Eric C. and Meyer, J{\"o}rg and Mun, Jungho and Patelli, Lorenzo and Pflug, Lukas and Rockstuhl, Carsten and Rho, Junsuk and Rotter, Stefan and Stout, Brian and T{\"o}rm{\"a}, P{\"a}ivi and Trigo, Jorge Olmos and Tristram, Frank and Tsitsas, Nikolaos L. and Vall{\´e}e, Renaud and Vynck, Kevin and Weiss, Thomas and Wiecha, Peter and Wriedt, Thomas and Yannopapas, Vassilios and Yurkin, Maxim A. and Zouros, Grigorios P.}, title = {T-matrix representation of optical scattering response: Suggestion for a data format}, volume = {333}, journal = {J. Quant. Spectrosc. Radiat. Transf.}, arxiv = {http://arxiv.org/abs/2408.10727}, doi = {10.1016/j.jqsrt.2024.109310}, pages = {109310}, year = {2025}, language = {en} } @article{RocheBetzYangetal.2024, author = {Roche, L{\´e}o J. and Betz, Fridtjof and Yang, Yuhui and Limame, Imad and Shih, Ching-Wen and Burger, Sven and Reitzenstein, Stephan}, title = {Numerical Investigation of a Coupled Micropillar - Waveguide System for Integrated Quantum Photonic Circuits}, volume = {7}, journal = {Adv. Quantum Technol.}, doi = {10.1002/qute.202400195}, pages = {2400195}, year = {2024}, language = {en} } @article{BinkowskiBurgerKewes2024, author = {Binkowski, Felix and Burger, Sven and Kewes, G{\"u}nter}, title = {A tiny Drude scatterer can accurately model a coherent emitter in nanophotonics}, volume = {13}, journal = {Nanophotonics}, doi = {10.1515/nanoph-2024-0170}, pages = {4537}, year = {2024}, language = {en} } @article{BernsYildizWinkelmannetal.2025, author = {Berns, Manon and Yildiz, Mirza and Winkelmann, Stefanie and Walter, Alexander}, title = {Independently engaging protein tethers of different length enhance synaptic vesicle trafficking to the plasma membrane}, volume = {603}, journal = {The Journal of Physiology}, number = {20}, doi = {10.1113/JP286651}, pages = {6107 -- 6134}, year = {2025}, abstract = {Synaptic vesicle (SV) trafficking toward the plasma membrane (PM) and subsequent SV maturation are essential for neurotransmitter release. These processes, including SV docking and priming, are coordinated by various proteins, such as SNAREs, Munc13, and Synaptotagmin (Syt), which connect—tether—the SV to the PM. Here, we investigated how tethers of varying lengths mediate SV docking using a simplified mathematical model. The heights of the three tether types—estimated from the structures of the SNARE complex, Munc13, and Syt—defined the SV-to-PM distance ranges for tether formation. Geometric considerations linked SV-to-PM distances to the probability and rate of tether formation. We assumed that SV tethering constrains SV motility and that multiple tethers associate by independent interactions. The model predicted that forming multiple tethers favors shorter SV-to-PM distances. Although tethers acted independently in the model, their geometrical properties often caused sequential assembly, from longer ones (Munc13/Syt), that accelerated SV movement towards the PM, to shorter ones (SNAREs) which stabilized PM-proximal SVs. Modifying tether lengths or numbers affected SV trafficking. The independent implementation of tethering proteins enabled their selective removal to mimic gene knockout situations. This showed that simulated SV-to-PM distance distributions qualitatively aligned with published EM studies upon removal of SNARE and Syt tethers, while Munc13 knockout data were best approximated when assuming additional disruption of SNARE tethers. Thus, while salient features of SV docking can be accounted for by independent tethering alone, our results suggest that functional tether interactions not yet featured in our model are crucial for biological function.}, language = {en} } @misc{BinkowskiBetzHammerschmidtetal.2024, author = {Binkowski, Felix and Betz, Fridtjof and Hammerschmidt, Martin and Zschiedrich, Lin and Burger, Sven}, title = {Source code and simulation results: Resonance modes in microstructured photonic waveguides - Efficient and accurate computation based on AAA rational approximation}, journal = {Zenodo}, doi = {10.5281/zenodo.14202408}, pages = {doi: 10.5281/zenodo.14202408}, year = {2024}, language = {en} } @article{BecksLippoldWinkleretal.2024, author = {Becks, Henrik and Lippold, Lukas and Winkler, Paul and Rohrer, Maximilian and Leusmann, Thorsten and Anton, David and Sprenger, Bjarne and K{\"a}hler, Philipp and Rudenko, Iryna and Andr{\´e}s Arcones, Daniel and Koutsourelakis, Phaedon-Stelios and Unger, J{\"o}rg F. and Weiser, Martin and Petryna, Yuri and Schnellenbach-Held, Martina and Lowke, Dirk and Wessels, Henning and Lenzen, Armin and Zabel, Volkmar and K{\"o}nke, Carsten and Claßen, Martin and Hegger, Josef}, title = {Neuartige Konzepte f{\"u}r die Zustands{\"u}berwachung und -analyse von Br{\"u}ckenbauwerken - Einblicke in das Forschungsvorhaben SPP100+}, volume = {99}, journal = {Bauingenieur}, number = {10}, doi = {10.37544/0005-6650-2024-10-63}, pages = {327 -- 338}, year = {2024}, abstract = {Die Br{\"u}ckeninfrastruktur in Deutschland und Europa steht aufgrund steigender Verkehrslasten und alternder Bauwerke vor erheblichen Herausforderungen. Das DFG-Schwerpunktprogramm 2388 „Hundert plus - Verl{\"a}ngerung der Lebensdauer komplexer Baustrukturen durch intelligente Digitalisierung" (SPP100+) strebt an, durch digitale Innovationen und pr{\"a}diktive Instandhaltungsstrategien die Nutzungsdauer bestehender Br{\"u}ckenbauwerke zu verl{\"a}ngern. Der vorliegende Beitrag fokussiert sich auf das SPP100+ zugeh{\"o}rige Cluster „Monitoring und Simulation", das sieben Teilprojekte umfasst. Die Projekte entwickeln fortschrittliche Methoden zur {\"U}berwachung und Zustandsbewertung von Br{\"u}cken mittels Digitaler Zwillinge, hochaufl{\"o}sender Sensortechnik und numerischer Simulationen. Innovative Ans{\"a}tze wie nichtlineare Modellanpassungen, stochastische Methoden und k{\"u}nstliche Intelligenz erm{\"o}glichen eine pr{\"a}zise und fr{\"u}hzeitige Identifizierung potenzieller Sch{\"a}den. Die Kombination aus kontinuierlichem Bauwerksmonitoring und effizienter Datenauswertung ist entscheidend f{\"u}r die langfristige Sicherheit und Langlebigkeit bestehender Br{\"u}cken und tr{\"a}gt dar{\"u}ber hinaus zur Ressourcenschonung bei.}, language = {de} } @article{GoebelHuynhCheginietal.2025, author = {G{\"o}bel, Fritz and Huynh, Ngoc Mai Monica and Chegini, Fatemeh and Pavarino, Luca and Weiser, Martin and Scacchi, Simone and Anzt, Hartwig}, title = {A BDDC Preconditioner for the Cardiac EMI Model in three Dimensions}, journal = {SIAM J. Sci. Comput.}, arxiv = {http://arxiv.org/abs/2502.07722}, year = {2025}, abstract = {We analyze a Balancing Domain Decomposition by Constraints (BDDC) preconditioner for the solution of three dimensional composite Discontinuous Galerkin discretizations of reaction-diffusion systems of ordinary and partial differential equations arising in cardiac cell-by-cell models like the Extracellular space, Membrane and Intracellular space (EMI) Model. These microscopic models are essential for the understanding of events in aging and structurally diseased hearts which macroscopic models relying on homogenized descriptions of the cardiac tissue, like Monodomain and Bidomain models, fail to adequately represent. The modeling of each individual cardiac cell results in discontinuous global solutions across cell boundaries, requiring the careful construction of dual and primal spaces for the BDDC preconditioner. We provide a scalable condition number bound for the precondition operator and validate the theoretical results with extensive numerical experiments.}, language = {en} } @article{BetzBinkowskiFischbachetal.2025, author = {Betz, Fridtjof and Binkowski, Felix and Fischbach, Jan David and Feldman, Nick and Zschiedrich, Lin and Rockstuhl, Carsten and Koenderink, A. Femius and Burger, Sven}, title = {Uncovering hidden resonances in non-Hermitian systems with scattering thresholds}, volume = {19}, journal = {Laser Photonics Rev.}, arxiv = {http://arxiv.org/abs/2503.03549}, doi = {10.1002/lpor.202500811}, pages = {e00811}, year = {2025}, language = {en} } @misc{BetzBinkowskiFischbachetal.2025, author = {Betz, Fridtjof and Binkowski, Felix and Fischbach, Jan David and Feldman, Nick and Rockstuhl, Carsten and Koenderink, A. Femius and Burger, Sven}, title = {Source code and simulation results: Hidden resonances in non-Hermitian systems with scattering thresholds}, journal = {Zenodo}, doi = {10.5281/zenodo.14651612}, pages = {doi: 10.5281/zenodo.14651612}, year = {2025}, language = {en} } @article{MukherjeeBurgerSiefkeetal.2025, author = {Mukherjee, Deshabrato and Burger, Sven and Siefke, Thomas and Gour, Jeetendra and Bodermann, Bernd and Petrik, Peter}, title = {Spectroscopic Ellipsometry of Plasmonic Gratings─Ideal Parameters for Sensing and Subpicometer Measurement Uncertainty}, volume = {10}, journal = {ACS Omega}, number = {14}, doi = {10.1021/acsomega.5c00951}, pages = {14466 -- 14473}, year = {2025}, language = {en} } @article{BlaskovicConradKlusetal.2025, author = {Blaskovic, Filip and Conrad, Tim and Klus, Stefan and Djurdjevac Conrad, Natasa}, title = {Random walk based snapshot clustering for detecting community dynamics in temporal networks}, volume = {15}, journal = {Scientific Reports}, arxiv = {http://arxiv.org/abs/2412.12187}, doi = {10.1038/s41598-025-09340-0}, pages = {24414}, year = {2025}, abstract = {The evolution of many dynamical systems that describe relationships or interactions between objects can be effectively modeled by temporal networks, which are typically represented as a sequence of static network snapshots. In this paper, we introduce a novel random walk based approach that can identify clusters of time-snapshots in which network community structures are stable. This allows to detect significant structural shifts over time, such as the splitting, merging, birth, or death of communities. We also provide a low-dimensional representation of entire snapshots, placing those with similar community structure close to each other in the feature space. To validate our approach, we develop an agent-based algorithm that generates synthetic datasets with the desired characteristic properties, enabling thorough testing and benchmarking. We further demonstrate the effectiveness and broad applicability of our technique by testing it on various social dynamics models and real-world datasets and comparing its performance to several state-of-the-art algorithms. Our findings highlight the strength of our approach to correctly capture and analyze the dynamics of complex systems.}, language = {en} } @phdthesis{Ernst2024, author = {Ernst, Ariane}, title = {Mathematical modeling and analysis of neurotransmission}, year = {2024}, abstract = {Modeling and simulation of neurotransmission plays a central role in the scientific investigation of synaptic functioning and neuronal communication. Understanding the neurotransmission process is crucial due to its fundamental significance in cognitive function, with impairments in this process potentially giving rise to severe pathological conditions. Existing modeling approaches capture the dynamic behavior and the probabilistic properties of the synaptic machinery utilizing results from stochastic chemical kinetics. However, the underlying mathematical theory rarely receives detailed consideration. In this thesis, we explore the neurotransmission process from a mathematical perspective and provide important insights that improve efficiency in its modeling and simulation. We introduce a new method for the direct and exact computation of first- and second-order moments of the postsynaptic current for the case of linear reaction networks, circumventing previously employed stochastic simulations. The approach hinges on the computation of the cross-correlation functions for the associated Markov jump process and their characterization by a partial differential equation. Our method can be applied to efficiently compare coarse-graining strategies for neurotransmission models, which we demonstrate for a significant recent model of synaptic vesicle release. We also numerically analyze the feasibility of reducing this particular model and show that a reduction can preserve the characteristics of the mean output current and its standard deviation to a satisfactory degree under typical stimulation conditions, where the approximation error can even be neglected depending on release site position. As the dependency on the local calcium concentration is preserved in the reduced model, it can be subjected to arbitrary types of signals in future studies. Moreover, we investigate the recovery processes of synaptic vesicles and release sites by introducing a nonlinear model with explicit recovery reactions. A sensitivity analysis provides the novel insight that the widely debated identity of the limiting recovery process during sustained stimulation is time-dependent. For our model, the output current's first-order moment and its deterministic approximation show an exceptionally high level of agreement. We determine this to be an inherent consequence of the model structure due to the independence of the two recovery processes, supporting future use of the deterministic approximation. Parameter estimations confirm our model's capability of reproducing experimental data.}, language = {en} } @article{delRazoDelleSite2025, author = {del Razo, Mauricio and Delle Site, Luigi}, title = {Dynamics of systems with varying number of particles: from Liouville equations to general master equations for open systems}, volume = {18, 001}, journal = {SciPost Physics}, doi = {10.21468/SciPostPhys.18.1.001}, year = {2025}, abstract = {A varying number of particles is one of the most relevant characteristics of systems of interest in nature and technology, ranging from the exchange of energy and matter with the surrounding environment to the change of particle number through internal dynamics such as reactions. The physico-mathematical modeling of these systems is extremely challenging, with the major difficulty being the time dependence of the number of degrees of freedom and the additional constraint that the increment or reduction of the number and species of particles must not violate basic physical laws. Theoretical models, in such a case, represent the key tool for the design of computational strategies for numerical studies that deliver trustful results. In this manuscript, we review complementary physico-mathematical approaches of varying number of particles inspired by rather different specific numerical goals. As a result of the analysis on the underlying common structure of these models, we propose a unifying master equation for general dynamical systems with varying number of particles. This equation embeds all the previous models and can potentially model a much larger range of complex systems, ranging from molecular to social agent-based dynamics.}, language = {en} } @article{AndresArconesWeiserKoutsourelakisetal.2024, author = {Andr{\´e}s Arcones, Daniel and Weiser, Martin and Koutsourelakis, Phaedon-Stelios and Unger, J{\"o}rg F.}, title = {Bias Identification Approaches for Model Updating of Simulation-based Digital Twins of Bridges}, volume = {2}, journal = {Structural Health Monitoring in the Light of Climate Impact and Data Science. Research and Review Journal of Nondestructive Testing}, number = {2}, doi = {10.58286/30524}, year = {2024}, abstract = {Simulation-based digital twins of bridges have the potential not only to serve as monitoring devices of the current state of the structure but also to generate new knowledge through physical predictions that allow for better-informed decisionmaking. For an accurate representation of the bridge, the underlying models must be tuned to reproduce the real system. Nevertheless, the necessary assumptions and simplifications in these models irremediably introduce discrepancies between measurements and model response. We will show that quantifying the extent of the uncertainties introduced through the models that lead to such discrepancies provides a better understanding of the real system, enhances the model updating process, and creates more robust and trustworthy digital twins. The inclusion of an explicit bias term will be applied to a representative demonstrator case based on the thermal response of the Nibelungenbr{\"u}cke of Worms. The findings from this work are englobed in the initiative SPP 100+, whose main aim is the extension of the service life of structures, especially through the implementation of digital twins.}, language = {en} } @article{BinkowskiBetzHammerschmidtetal.2025, author = {Binkowski, Felix and Betz, Fridtjof and Hammerschmidt, Martin and Zschiedrich, Lin and Burger, Sven}, title = {Resonance modes in microstructured photonic waveguides: Efficient and accurate computation based on AAA rational approximation}, volume = {14}, journal = {Nanophotonics}, arxiv = {http://arxiv.org/abs/2412.13826}, doi = {10.1515/nanoph-2024-0755}, pages = {1665}, year = {2025}, language = {en} } @inproceedings{SchaibleWinartoSkorjancetal.2025, author = {Schaible, Jonas and Winarto, Hanifah and Skorjanc, Victor and Yoo, Danbi and Zimmermann, Lea and Wessels, Andreas and J{\"a}ger, Klaus and Sekulic, Ivan and Schneider, Philipp-Immanuel and Bl{\"a}si, Benedikt and Burger, Sven and Becker, Christiane}, title = {Optimization strategies for colorful thin film solar cells}, volume = {PC13361}, booktitle = {Proc. SPIE}, doi = {10.1117/12.3041408}, pages = {PC133610E}, year = {2025}, language = {en} } @article{JaegerAeberhardAlarconLladoetal.2025, author = {J{\"a}ger, Klaus and Aeberhard, Urs and Alarcon Llado, Esther and Bl{\"a}si, Benedikt and Burger, Sven and Ehrler, Bruno and Favre, Wilfried and Fejfar, Anton{\´i}n and Gageot, Tristan and Gordon, Ivan and Helmers, Henning and H{\"o}hn, Oliver and Isabella, Olindo and Jošt, Marko and Ledinsk{\´y}, Martin and Mandal, Jyotirmoy and Manley, Phillip and Mu{\~n}oz, Delfina and Omair, Zunaid and Ortiz Lizcano, Juan Camilo and Paetzold, Ulrich W. and Raman, Aaswath P. and Sai, Hitoshi and Saive, Rebecca and Schmid, Martina and Yablonovitch, Eli and Becker, Christiane}, title = {Optics for terawatt-scale photovoltaics: review and perspectives}, volume = {17}, journal = {Adv. Opt. Photonics}, number = {1}, publisher = {Optica Publishing Group}, issn = {1943-8206}, doi = {10.1364/AOP.530556}, pages = {185 -- 294}, year = {2025}, abstract = {Photovoltaics, a mature technology, is set to play a vital role in achieving a carbon-free energy system. This article examines the pivotal role of optics in advancing photovoltaics. We identify key scientific research areas where the optics community can make significant contributions. We are guided by the central question: How can optics facilitate the large-scale deployment of photovoltaics necessary for decarbonizing our societies?}, language = {en} } @article{delRazoKostre2025, author = {del Razo, Mauricio and Kostr{\´e}, Margarita}, title = {Open reaction-diffusion systems: bridging probabilistic theory and simulations across scales}, volume = {58}, journal = {Journal of Physics A: Mathematical and Theoretical}, number = {14}, doi = {10.1088/1751-8121/adc520}, year = {2025}, abstract = {Reaction-diffusion processes are the foundational model for a diverse range of complex systems, ranging from biochemical reactions to social agent-based phenomena. The underlying dynamics of these systems occur at the individual particle/agent level, and in realistic applications, they often display interaction with their environment through energy or material exchange with a reservoir. This requires intricate mathematical considerations, especially in the case of material exchange since the varying number of particles/agents results in ``on-the-fly'' modification of the system dimension. In this work, we first overview the probabilistic description of reaction-diffusion processes at the particle level, which readily handles varying number of particles. We then extend this model to consistently incorporate interactions with macroscopic material reservoirs. Based on the resulting expressions, we bridge the probabilistic description with macroscopic concentration-based descriptions for linear and nonlinear reaction-diffusion systems, as well as for an archetypal open reaction-diffusion system. Using these mathematical bridges across scales, we finally develop numerical schemes for open reaction-diffusion systems, which we implement in two illustrative examples. This work establishes a methodological workflow to bridge particle-based probabilistic descriptions with macroscopic concentration-based descriptions of reaction-diffusion in open settings, laying the foundations for a multiscale theoretical framework upon which to construct theory and simulation schemes that are consistent across scales.}, language = {en} } @article{BetzBinkowskiHammerschmidtetal.2023, author = {Betz, Fridtjof and Binkowski, Felix and Hammerschmidt, Martin and Zschiedrich, Lin and Burger, Sven}, title = {Cover Picture: Resonance Expansion of Quadratic Quantities with Regularized Quasinormal Modes}, volume = {220}, journal = {Phys. Status Solidi A}, doi = {10.1002/pssa.202370013}, pages = {2370013}, year = {2023}, language = {en} } @inproceedings{KuenBetzBinkowskietal.2023, author = {Kuen, Lilli and Betz, Fridtjof and Binkowski, Felix and Schneider, Philipp-Immanuel and Hammerschmidt, Martin and Heermeier, Niels and Rodt, Sven and Reitzenstein, Stephan and Burger, Sven}, title = {Applying a Riesz-projection-based contour integral eigenvalue solver to compute resonance modes of a VCSEL}, volume = {12575}, booktitle = {Proc. SPIE}, arxiv = {http://arxiv.org/abs/2306.02926}, doi = {10.1117/12.2665490}, pages = {125750J}, year = {2023}, language = {en} } @article{MikheevaColomAchourietal.2023, author = {Mikheeva, Elena and Colom, R{\´e}mi and Achouri, Karim and Overvig, Adam and Binkowski, Felix and Duboz, Jean-Yves and Cueff, S{\´e}bastien and Fan, Shanhui and Burger, Sven and Al{\`u}, Andrea and Genevet, Patrice}, title = {Asymmetric phase modulation with light with parity-symmetry broken metasurfaces}, volume = {10}, journal = {Optica}, doi = {10.1364/OPTICA.495681}, pages = {1287}, year = {2023}, language = {en} } @article{StraubeHoefling2024, author = {Straube, Arthur and H{\"o}fling, Felix}, title = {Depinning transition of self-propelled particles}, volume = {110}, journal = {Physical Review E}, number = {6}, arxiv = {http://arxiv.org/abs/2306.09150}, doi = {10.1103/PhysRevE.110.L062601}, pages = {L062601}, year = {2024}, abstract = {For self-propelled particles in a corrugated potential landscape, we describe a discontinuous change of the classical depinning transition and a host of unique behaviors sensitive to the persistence of the propulsion direction. Exact and semianalytic results for active Brownian particles corroborate a creep regime with a superexponentially suppressed drift velocity upon lowering the force towards the threshold value. This unusual nonlinear response emerges from the competition of two critical scaling laws with exponents of 1/2 for rapidly reorienting particles and 𝑑/2 for particles with a persistent orientation; the latter case depends on the dimensionality 𝑑 of rotational motion and also includes run-and-tumble particles. Additionally, different giant diffusion phenomena occur in the two regimes. Our findings extend to random dynamics with bounded noise near a saddle-node bifurcation and have potential applications in various nonequilibrium problems, including arrested active matter and cell migration.}, language = {en} } @article{MontefuscoHelfmannOkunolaetal.2024, author = {Montefusco, Alberto and Helfmann, Luzie and Okunola, Toluwani and Winkelmann, Stefanie and Sch{\"u}tte, Christof}, title = {Partial mean-field model for neurotransmission dynamics}, volume = {369}, journal = {Mathematical Biosciences}, arxiv = {http://arxiv.org/abs/2307.01737}, doi = {10.1016/j.mbs.2024.109143}, year = {2024}, abstract = {This article addresses reaction networks in which spatial and stochastic effects are of crucial importance. For such systems, particle-based models allow us to describe all microscopic details with high accuracy. However, they suffer from computational inefficiency if particle numbers and density get too large. Alternative coarse-grained-resolution models reduce computational effort tremendously, e.g., by replacing the particle distribution by a continuous concentration field governed by reaction-diffusion PDEs. We demonstrate how models on the different resolution levels can be combined into hybrid models that seamlessly combine the best of both worlds, describing molecular species with large copy numbers by macroscopic equations with spatial resolution while keeping the stochastic-spatial particle-based resolution level for the species with low copy numbers. To this end, we introduce a simple particle-based model for the binding dynamics of ions and vesicles at the heart of the neurotransmission process. Within this framework, we derive a novel hybrid model and present results from numerical experiments which demonstrate that the hybrid model allows for an accurate approximation of the full particle-based model in realistic scenarios.}, language = {en} } @article{NiemannKlusConradetal.2024, author = {Niemann, Jan-Hendrik and Klus, Stefan and Conrad, Natasa Djurdjevac and Sch{\"u}tte, Christof}, title = {Koopman-Based Surrogate Models for Multi-Objective Optimization of Agent-Based Systems}, volume = {460}, journal = {Physica D: Nonlinear Phenomena}, arxiv = {http://arxiv.org/abs/2306.17666}, doi = {https://doi.org/10.1016/j.physd.2024.134052}, pages = {134052}, year = {2024}, abstract = {Agent-based models (ABMs) provide an intuitive and powerful framework for studying social dynamics by modeling the interactions of individuals from the perspective of each individual. In addition to simulating and forecasting the dynamics of ABMs, the demand to solve optimization problems to support, for example, decision-making processes naturally arises. Most ABMs, however, are non-deterministic, high-dimensional dynamical systems, so objectives defined in terms of their behavior are computationally expensive. In particular, if the number of agents is large, evaluating the objective functions often becomes prohibitively time-consuming. We consider data-driven reduced models based on the Koopman generator to enable the efficient solution of multi-objective optimization problems involving ABMs. In a first step, we show how to obtain data-driven reduced models of non-deterministic dynamical systems (such as ABMs) that depend on potentially nonlinear control inputs. We then use them in the second step as surrogate models to solve multi-objective optimal control problems. We first illustrate our approach using the example of a voter model, where we compute optimal controls to steer the agents to a predetermined majority, and then using the example of an epidemic ABM, where we compute optimal containment strategies in a prototypical situation. We demonstrate that the surrogate models effectively approximate the Pareto-optimal points of the ABM dynamics by comparing the surrogate-based results with test points, where the objectives are evaluated using the ABM. Our results show that when objectives are defined by the dynamic behavior of ABMs, data-driven surrogate models support or even enable the solution of multi-objective optimization problems.}, language = {en} } @article{LueckeWinkelmannHeitzigetal.2024, author = {L{\"u}cke, Marvin and Winkelmann, Stefanie and Heitzig, Jobst and Molkenthin, Nora and Koltai, P{\´e}ter}, title = {Learning interpretable collective variables for spreading processes on networks}, volume = {109}, journal = {Physical Review E}, number = {2}, arxiv = {http://arxiv.org/abs/2307.03491}, doi = {10.1103/PhysRevE.109.L022301}, pages = {L022301}, year = {2024}, abstract = {Collective variables (CVs) are low-dimensional projections of high-dimensional system states. They are used to gain insights into complex emergent dynamical behaviors of processes on networks. The relation between CVs and network measures is not well understood and its derivation typically requires detailed knowledge of both the dynamical system and the network topology. In this Letter, we present a data-driven method for algorithmically learning and understanding CVs for binary-state spreading processes on networks of arbitrary topology. We demonstrate our method using four example networks: the stochastic block model, a ring-shaped graph, a random regular graph, and a scale-free network generated by the Albert-Barab{\´a}si model. Our results deliver evidence for the existence of low-dimensional CVs even in cases that are not yet understood theoretically.}, language = {en} } @misc{BinkowskiBetzColometal.2023, author = {Binkowski, Felix and Betz, Fridtjof and Colom, Remi and Genevet, Patrice and Burger, Sven}, title = {Source code and simulation results: Poles and zeros of electromagnetic quantities in photonic systems}, journal = {Zenodo}, doi = {10.5281/zenodo.8063931}, pages = {8063931}, year = {2023}, language = {en} } @article{BinkowskiBetzColometal.2024, author = {Binkowski, Felix and Betz, Fridtjof and Colom, Remi and Genevet, Patrice and Burger, Sven}, title = {Poles and zeros in non-Hermitian systems: Application to photonics}, volume = {109}, journal = {Phys. Rev. B}, arxiv = {http://arxiv.org/abs/2307.04654}, doi = {10.1103/PhysRevB.109.045414}, pages = {045414}, year = {2024}, language = {en} } @article{ZonkerPadillaIglesiasDjurdjevacConrad2023, author = {Zonker, Johannes and Padilla-Iglesias, Cecilia and Djurdjevac Conrad, Natasa}, title = {Insights into drivers of mobility and cultural dynamics of African hunter-gatherers over the past 120 000 years}, volume = {10}, journal = {Royal Society Open Science}, number = {11}, doi = {10.1098/rsos.230495}, year = {2023}, abstract = {Humans have a unique capacity to innovate, transmit and rely on complex, cumulative culture for survival. While an important body of work has attempted to explore the role of changes in the size and interconnectedness of populations in determining the persistence, diversity and complexity of material culture, results have achieved limited success in explaining the emergence and spatial distribution of cumulative culture over our evolutionary trajectory. Here, we develop a spatio-temporally explicit agent-based model to explore the role of environmentally driven changes in the population dynamics of hunter-gatherer communities in allowing the development, transmission and accumulation of complex culture. By modelling separately demography- and mobility-driven changes in interaction networks, we can assess the extent to which cultural change is driven by different types of population dynamics. We create and validate our model using empirical data from Central Africa spanning 120 000 years. We find that populations would have been able to maintain diverse and elaborate cultural repertoires despite abrupt environmental changes and demographic collapses by preventing isolation through mobility. However, we also reveal that the function of cultural features was also an essential determinant of the effects of environmental or demographic changes on their dynamics. Our work can therefore offer important insights into the role of a foraging lifestyle on the evolution of cumulative culture.}, language = {en} } @article{DjurdjevacConradChemnitzKostreetal.2024, author = {Djurdjevac Conrad, Natasa and Chemnitz, Robin and Kostre, Margarita and Schweigart, Fleur and Fless, Friederike and Sch{\"u}tte, Christof and Ducke, Benjamin}, title = {A Mathematical perspective on Romanisation: Modelling the Roman road activation process in ancient Tunisia}, volume = {19}, journal = {PLoS ONE}, number = {9}, doi = {10.1371/journal.pone.0309752}, year = {2024}, abstract = {Romanisation is a multi-faceted historical phenomenon with profound and lasting cultural impact on the ancient world. In the modern-day territory of Tunisia, this is particularly manifest during the first four centuries AD, under the reign of the Roman Empire. We derive a reduced, operational concept of Romanisation as a cultural diffusion process that is observable in the archaeological remains of the Roman era settlement system. We then introduce a novel mathematical model that computes spatio-temporal approximations for the Romanisation of the settlement system. The model is based on the concept of temporal road activation and makes minimal assumptions regarding input data quality. The results of our study contribute to the understanding of the time dynamics of the region's road network, under the influence of Romanisation. Our model can be applied in similar archaeological research scenarios, to generate spatio-temporal backbones for the analysis of otherwise intractably complex social processes.}, language = {en} } @misc{BetzBinkowskiBurger2023, author = {Betz, Fridtjof and Binkowski, Felix and Burger, Sven}, title = {RPExpand (Version 1)}, journal = {Zenodo}, doi = {10.5281/zenodo.7840116}, pages = {doi: 10.5281/zenodo.7840116}, year = {2023}, language = {en} } @article{ErnstBankowskiJusyteetal.2025, author = {Ernst, Ariane and Bankowski, Anastasia and Jusyte, Meida and Okunola, Toluwani and Petrov, Tino and Walter, Alexander and Winkelmann, Stefanie}, title = {Parameter Optimization for a Neurotransmission Recovery Model}, volume = {87}, journal = {Bulletin of Mathematical Biology}, publisher = {Bulletin of Mathematical Biology}, doi = {10.1007/s11538-025-01486-2}, year = {2025}, abstract = {We assess the empirical applicability of a simplified model for neurotransmitter release that incorporates maturation, fusion, and recovery of both release sites and vesicles. Model parameters are optimized by fitting the model to experimental data obtained from neuromuscular junction synapses of 3rd-instar Drosophila melanogaster larvae. In particular, the mean-squared error between the local extrema of the simulated total junction current and its experimental counterpart is minimized. We compare three estimation approaches, differing in the choice of optimized parameters and the fusion rate function. Despite the model's minimalistic structure, it demonstrates a compelling ability to replicate experimental data, yielding plausible parameter estimates for five different animals. An additional identifiability analysis based on the profile likelihood reveals practical non-identifiabilities for several parameters, highlighting the need for additional constraints or data to improve estimation accuracy.}, language = {en} } @inproceedings{SekulicSchneiderHammerschmidtetal.2025, author = {Sekulic, Ivan and Schneider, Philipp-Immanuel and Hammerschmidt, Martin and Schaible, Jonas and Burger, Sven}, title = {Physics informed Bayesian optimization for inverse design of diffractive optical elements}, volume = {PC13573}, booktitle = {Proc. SPIE}, doi = {10.1117/12.3064372}, pages = {PC135730R}, year = {2025}, language = {en} } @inproceedings{HammerschmidtPlockBurgeretal.2025, author = {Hammerschmidt, Martin and Plock, Matthias and Burger, Sven and Truong, Vinh and Soltwisch, Victor and Schneider, Philipp-Immanuel}, title = {Machine learning approach for full Bayesian parameter reconstruction}, volume = {13568}, booktitle = {Proc. SPIE}, doi = {10.1117/12.3062268}, pages = {1356806}, year = {2025}, language = {en} } @article{BinkowskiKoulasSimosBetzetal.2025, author = {Binkowski, Felix and Koulas-Simos, Aris and Betz, Fridtjof and Plock, Matthias and Sekulic, Ivan and Manley, Phillip and Hammerschmidt, Martin and Schneider, Philipp-Immanuel and Zschiedrich, Lin and Munkhbat, Battulga and Reitzenstein, Stephan and Burger, Sven}, title = {High Purcell enhancement in all-TMDC nanobeam resonator designs with active monolayers for nanolasers}, volume = {112}, journal = {Phys. Rev. B}, arxiv = {http://arxiv.org/abs/2508.05333}, doi = {10.1103/nxh9-dhvx}, pages = {235410}, year = {2025}, language = {en} } @misc{BinkowskiKoulasSimosBetzetal.2025, author = {Binkowski, Felix and Koulas-Simos, Aris and Betz, Fridtjof and Plock, Matthias and Sekulic, Ivan and Manley, Phillip and Hammerschmidt, Martin and Schneider, Philipp-Immanuel and Zschiedrich, Lin and Munkhbat, Battulga and Reitzenstein, Stephan and Burger, Sven}, title = {Source code and simulation results: High Purcell enhancement in all-TMDC nanobeam resonator designs with active monolayers for nanolasers}, journal = {Zenodo}, doi = {10.5281/zenodo.16533803}, year = {2025}, language = {en} } @article{StraubeOliconMendezWinkelmannetal.2025, author = {Straube, Arthur and Olic{\´o}n M{\´e}ndez, Guillermo and Winkelmann, Stefanie and H{\"o}fling, Felix and Engel, Maximilian}, title = {Unfolding the geometric structure and multiple timescales of the urea-urease pH oscillator}, arxiv = {http://arxiv.org/abs/2508.07275}, year = {2025}, abstract = {We study a two-variable dynamical system modeling pH oscillations in the urea-urease reaction within giant lipid vesicles - a problem that intrinsically contains multiple, well-separated timescales. Building on an existing, deterministic formulation via ordinary differential equations, we resolve different orders of magnitude within a small parameter and analyze the system's limit cycle behavior using geometric singular perturbation theory (GSPT). By introducing two different coordinate scalings - each valid in a distinct region of the phase space - we resolve the local dynamics near critical fold points, using the extension of GSPT through such singular points due to Krupa and Szmolyan. This framework enables a geometric decomposition of the periodic orbits into slow and fast segments and yields closed-form estimates for the period of oscillation. In particular, we link the existence of such oscillations to an underlying biochemical asymmetry, namely, the differential transport across the vesicle membrane.}, language = {en} } @article{KourovSamoilovaStraube2025, author = {Kourov, Mikhail N. and Samoilova, Anna E. and Straube, Arthur}, title = {Dynamics of a chain of interacting magnetic particles in a one-dimensional periodic energy landscape}, volume = {89}, journal = {Bull. Russ. Acad. Sci. Phys.}, number = {7}, issn = {1062-8738}, doi = {10.1134/S1062873825711742}, pages = {1086 -- 1092}, year = {2025}, abstract = {We explore the dynamics of a one-dimensional chain of paramagnetic colloidal particles in a periodic potential. The model accounts for a constant external force, along with magnetic dipolar attraction and hard-core repulsive interactions between particles. Numerical simulations reveal the emergence of a traveling kink - a chain defect propagating along the chain. We show that the kink emerges beyond a critical force threshold and identify parameter regimes corresponding to distinct dynamic modes such as a pinned kink, a running kink, a cluster kink, and chain drift.}, language = {en} } @misc{OPUS4-10176, title = {Mathematical Optimization for Machine Learning}, editor = {Fackeldey, Konstantin and Kannan, Aswin and Pokutta, Sebastian and Sharma, Kartikey and Walter, Daniel and Walter, Andrea and Weiser, Martin}, publisher = {De Gruyter}, isbn = {9783111376776}, doi = {10.1515/9783111376776}, year = {2025}, abstract = {Mathematical optimization and machine learning are closely related. This proceedings volume of the Thematic Einstein Semester 2023 of the Berlin Mathematics Research Center MATH+ collects recent progress on their interplay in topics such as discrete optimization, nonlinear programming, optimal control, first-order methods, multilevel optimization, machine learning in optimization, physics-informed learning, and fairness in machine learning.}, language = {en} } @inproceedings{SchneiderSekulicPlocketal.2025, author = {Schneider, Philipp-Immanuel and Sekulic, Ivan and Plock, Matthias and Hammerschmidt, Martin and Rodt, Sven and Reitzenstein, Stephan and Burger, Sven}, title = {Physics-informed Bayesian optimization of nanophotonic devices}, volume = {IPRSN}, booktitle = {Advanced Photonics Congress}, doi = {10.1364/IPRSN.2025.ITu1A.2}, pages = {ITu1A.2}, year = {2025}, language = {en} } @inproceedings{JaegerMandalRandetal.2025, author = {J{\"a}ger, Klaus and Mandal, Jyotirmoy and Rand, Barry P. and Meggers, Forrest and Becker, Christiane}, title = {Thermal Management of Solar Modules with Infrared-Antireflective Coatings}, volume = {SOLITH}, booktitle = {Advanced Photonics Congress}, doi = {10.1364/SOLITH.2025.SM4E.2}, pages = {SM4E.2}, year = {2025}, language = {en} } @article{TillmannBlaesiBurgeretal.2021, author = {Tillmann, Peter and Bl{\"a}si, Benedikt and Burger, Sven and Hammerschmidt, Martin and H{\"o}hn, Oliver and Becker, Christiane and J{\"a}ger, Klaus}, title = {Optimizing metal grating back reflectors for III-V-on-silicon multijunction solar cells}, volume = {29}, journal = {Opt. Express}, doi = {10.1364/OE.426761}, pages = {22517}, year = {2021}, language = {en} } @misc{RaharinirinaWeberBirketal.2021, author = {Raharinirina, N. Alexia and Weber, Marcus and Birk, Ralph and Fackeldey, Konstantin and Klasse, Sarah M. and Richter, Tonio Sebastian}, title = {Different Tools and Results for Correspondence Analysis}, doi = {10.12752/8257}, year = {2021}, abstract = {This is a list of codes generated from ancient egyptian texts. The codes are used for a correspondence analysis (CA). Codes and CA software are available from the linked webpage.}, language = {en} } @article{PlockBurgerSchneider2021, author = {Plock, Matthias and Burger, Sven and Schneider, Philipp-Immanuel}, title = {Recent advances in Bayesian optimization with applications to parameter reconstruction in optical nano-metrology}, volume = {11783}, journal = {Proc. SPIE}, arxiv = {http://arxiv.org/abs/2107.05499}, doi = {10.1117/12.2592266}, pages = {117830J}, year = {2021}, language = {en} } @article{WinkelmannZonkerSchuetteetal.2021, author = {Winkelmann, Stefanie and Zonker, Johannes and Sch{\"u}tte, Christof and Djurdjevac Conrad, Natasa}, title = {Mathematical modeling of spatio-temporal population dynamics and application to epidemic spreading}, volume = {336}, journal = {Mathematical Biosciences}, publisher = {Elsevier}, arxiv = {http://arxiv.org/abs/2205.05000}, doi = {10.1016/j.mbs.2021.108619}, year = {2021}, abstract = {Agent based models (ABMs) are a useful tool for modeling spatio-temporal population dynamics, where many details can be included in the model description. Their computational cost though is very high and for stochastic ABMs a lot of individual simulations are required to sample quantities of interest. Especially, large numbers of agents render the sampling infeasible. Model reduction to a metapopulation model leads to a significant gain in computational efficiency, while preserving important dynamical properties. Based on a precise mathematical description of spatio-temporal ABMs, we present two different metapopulation approaches (stochastic and piecewise deterministic) and discuss the approximation steps between the different models within this framework. Especially, we show how the stochastic metapopulation model results from a Galerkin projection of the underlying ABM onto a finite-dimensional ansatz space. Finally, we utilize our modeling framework to provide a conceptual model for the spreading of COVID-19 that can be scaled to real-world scenarios.}, language = {en} } @article{AndrleHoenickeGwaltetal.2021, author = {Andrle, Anna and H{\"o}nicke, Philipp and Gwalt, Grzegorz and Schneider, Philipp-Immanuel and Kayser, Yves and Siewert, Frank and Soltwisch, Victor}, title = {GIXRF and machine learning as metrological tools for shape and element sensitive reconstructions of periodic nanostructures}, volume = {11611}, journal = {Proc. SPIE}, doi = {10.1117/12.2586082}, pages = {116110R}, year = {2021}, language = {en} } @article{NitzkeFackeldeyVrabec2021, author = {Nitzke, Isabel and Fackeldey, Konstantin and Vrabec, Jadran}, title = {Long range corrections for inhomogeneous fluids containing a droplet or a bubble}, journal = {Molecular Simulation}, doi = {https://doi.org/10.1080/08927022.2021.1954639}, pages = {1 -- 14}, year = {2021}, abstract = {Long range corrections for molecular simulations of inhomogeneous fluids with a spherical interface are presented. Correction terms for potential energy, force and virial are derived for the monatomic Lennard-Jones fluid. The method is generalised to the Mie potential and arbitrary molecular structures, employing a numerically efficient centre of mass cut-off scheme. The results are validated by a series of droplet simulations for one-centre and two-centre Lennard-Jones fluids with different cut-off radii rc. Systems with rc=8σ provide a check of self-consistence. Further, a system containing a bubble is investigated for the one-centre Lennard-Jones fluid. The equilibrium properties are almost completely independent on the cut-off radius. In comparison with vapour-liquid equilibrium data for systems without a curved interface, all properties show the expected behaviour. Simulation data are used to approximate the surface tension, which is in good agreement with the findings for planar interfaces, thus verifying the present corrections.}, language = {en} } @article{AndrleHoenickeGwaltetal.2021, author = {Andrle, Anna and H{\"o}nicke, Philipp and Gwalt, Grzegorz and Schneider, Philipp-Immanuel and Kayser, Yves and Siewert, Frank and Soltwisch, Victor}, title = {Shape- and Element-Sensitive Reconstruction of Periodic Nanostructures with Grazing Incidence X-ray Fluorescence Analysis and Machine Learning}, volume = {11}, journal = {Nanomaterials}, doi = {10.3390/nano11071647}, pages = {1647}, year = {2021}, language = {en} } @article{TiernoJohansenStraube2021, author = {Tierno, Pietro and Johansen, Tom H. and Straube, Arthur}, title = {Thermally active nanoparticle clusters enslaved by engineered domain wall traps}, volume = {12}, journal = {Nature Commun.}, doi = {10.1038/s41467-021-25931-7}, pages = {5813}, year = {2021}, abstract = {The stable assembly of fluctuating nanoparticle clusters on a surface represents a technological challenge of widespread interest for both fundamental and applied research. Here we demonstrate a technique to stably confine in two dimensions clusters of interacting nanoparticles via size-tunable, virtual magnetic traps. We use cylindrical Bloch walls arranged to form a triangular lattice of ferromagnetic domains within an epitaxially grown ferrite garnet film. At each domain, the magnetic stray field generates an effective harmonic potential with a field tunable stifness. The experiments are combined with theory to show that the magnetic confinement is effectively harmonic and pairwise interactions are of dipolar nature, leading to central, strictly repulsive forces. For clusters of magnetic nanoparticles, the stationary collective states arise from the competition between repulsion, confinement and the tendency to fill the central potential well. Using a numerical simulation model as a quantitative map between the experiment and theory we explore the field-induced crystallization process for larger clusters and unveil the existence of three different dynamical regimes. The present method provides a model platform for investigations of the collective phenomena emerging when strongly confined nanoparticle clusters are forced to move in an idealized, harmonic-like potential.}, language = {en} } @article{OehmeMoewisBoethetal.2022, author = {Oehme, Stephan and Moewis, Philippe and Boeth, Heide and Bartek, Benjamin and Lippert, Annika and von Tycowicz, Christoph and Ehrig, Rainald and Duda, Georg and Jung, Tobias}, title = {PCL insufficient patients with increased translational and rotational passive knee joint laxity have no increased range of anterior-posterior and rotational tibiofemoral motion during level walking}, volume = {12}, journal = {Scientific Reports}, number = {1}, doi = {10.1038/s41598-022-17328-3}, pages = {1 -- 11}, year = {2022}, language = {en} } @inproceedings{TillmannJaegerKatzetal.2021, author = {Tillmann, Peter and J{\"a}ger, Klaus and Katz, Eugene and Becker, Christiane}, title = {Relaxed current-matching constraints by bifacial operation and luminescent coupling in perovskite/silicon tandem solar cells}, booktitle = {2021 IEEE 48th Photovoltaic Specialists Conference (PVSC)}, doi = {10.1109/PVSC43889.2021.9518891}, pages = {1086}, year = {2021}, language = {en} } @misc{BetzBinkowskiBurger2021, author = {Betz, Fridtjof and Binkowski, Felix and Burger, Sven}, title = {RPExpand: Software for Riesz projection expansion of resonance phenomena [Source Code]}, doi = {10.24433/CO.2372084.v1}, year = {2021}, language = {de} } @article{WuArrivaultDurufleetal.2021, author = {Wu, Tong and Arrivault, Denis and Durufl{\´e}, Marc and Gras, Alexandre and Binkowski, Felix and Burger, Sven and Yan, Wei and Lalanne, Philippe}, title = {Efficient hybrid method for the modal analysis of optical microcavities and nanoresonators}, volume = {38}, journal = {J. Opt. Soc. Am. A}, doi = {10.1364/JOSAA.428224}, pages = {1224}, year = {2021}, language = {en} } @article{BetzBinkowskiBurger2021, author = {Betz, Fridtjof and Binkowski, Felix and Burger, Sven}, title = {RPExpand: Software for Riesz projection expansion of resonance phenomena}, volume = {15}, journal = {SoftwareX}, doi = {10.1016/j.softx.2021.100763}, pages = {100763}, year = {2021}, language = {en} } @article{NegrinMonteceloMovsesyanGaoetal.2022, author = {Negrin-Montecelo, Yoel and Movsesyan, Artur and Gao, Jie and Burger, Sven and Wang, Zhiming and Nlate, Sylvain and Pouget, Emilie and Oda, Reiko and Comesana-Hermo, Miguel and Govorov, Alexander O. and Correa-Duarte, Miguel}, title = {Chiral Generation of Hot Carriers for Polarization-Sensitive Plasmonic Photocatalysis with Hybrid Nanostructures}, volume = {144}, journal = {J. Am. Chem. Soc.}, doi = {10.1021/jacs.1c10526}, pages = {1663}, year = {2022}, language = {en} } @inproceedings{SchnauberSchallBounouaretal.2021, author = {Schnauber, Peter and Schall, Johannes and Bounouar, Samir and Srinivasan, Kartik and Davanco, Marcelo and Song, Jin-Dong and Burger, Sven and Rodt, Sven and Reitzenstein, Stephan}, title = {Deterministically fabricated quantum dot - waveguide systems for on-chip quantum optics}, volume = {11806}, booktitle = {Proc. SPIE}, doi = {10.1117/12.2596042}, pages = {118060G}, year = {2021}, language = {en} } @inproceedings{PerevoznikBoseBurgeretal.2021, author = {Perevoznik, Dmitrii and Bose, Surajit and Burger, Sven and Demircan, Ayhan and Morgner, Uwe}, title = {Writing Photonic Components in Polymers Using Femtosecond Pulses}, booktitle = {Conference on Lasers and Electro-Optics (CLEO)}, doi = {10.1364/CLEO_AT.2021.ATh4P.4}, pages = {ATh4P.4}, year = {2021}, language = {en} } @article{delRazoFroembergStraubeetal.2022, author = {del Razo, Mauricio and Fr{\"o}mberg, Daniela and Straube, Arthur and Sch{\"u}tte, Christof and H{\"o}fling, Felix and Winkelmann, Stefanie}, title = {A probabilistic framework for particle-based reaction-diffusion dynamics using classical Fock space representations}, volume = {112}, journal = {Letters in Mathematical Physics}, number = {49}, arxiv = {http://arxiv.org/abs/arXiv:2109.13616}, doi = {10.1007/s11005-022-01539-w}, year = {2022}, language = {en} } @article{StraubeWinkelmannSchuetteetal.2021, author = {Straube, Arthur and Winkelmann, Stefanie and Sch{\"u}tte, Christof and H{\"o}fling, Felix}, title = {Stochastic pH oscillations in a model of the urea-urease reaction confined to lipid vesicles}, volume = {12}, journal = {J. Phys. Chem. Lett.}, doi = {10.1021/acs.jpclett.1c03016}, pages = {9888 -- 9893}, year = {2021}, abstract = {The urea-urease clock reaction is a pH switch from acid to basic that can turn into a pH oscillator if it occurs inside a suitable open reactor. We numerically study the confinement of the reaction to lipid vesicles, which permit the exchange with an external reservoir by differential transport, enabling the recovery of the pH level and yielding a constant supply of urea molecules. For microscopically small vesicles, the discreteness of the number of molecules requires a stochastic treatment of the reaction dynamics. Our analysis shows that intrinsic noise induces a significant statistical variation of the oscillation period, which increases as the vesicles become smaller. The mean period, however, is found to be remarkably robust for vesicle sizes down to approximately 200 nm, but the periodicity of the rhythm is gradually destroyed for smaller vesicles. The observed oscillations are explained as a canard-like limit cycle that differs from the wide class of conventional feedback oscillators.}, language = {en} } @article{BetzBinkowskiHammerschmidtetal.2023, author = {Betz, Fridtjof and Binkowski, Felix and Hammerschmidt, Martin and Zschiedrich, Lin and Burger, Sven}, title = {Resonance expansion of quadratic quantities with regularized quasinormal modes}, volume = {220}, journal = {Phys. Status Solidi A}, arxiv = {http://arxiv.org/abs/2212.11117}, doi = {10.1002/pssa.202200892}, pages = {2200892}, year = {2023}, language = {en} } @article{BenSoltaneColomStoutetal.2023, author = {Ben Soltane, Isam and Colom, R{\´e}mi and Stout, Brian and Bonod, Nicolas}, title = {Derivation of the Transient and Steady Optical States from the Poles of the S-Matrix}, volume = {17}, journal = {Laser Photon. Rev.}, doi = {10.1002/lpor.202200141}, pages = {2200141}, year = {2023}, language = {en} } @article{HelfmannConradLorenzSpreenetal.2023, author = {Helfmann, Luzie and Conrad, Natasa Djurdjevac and Lorenz-Spreen, Philipp and Sch{\"u}tte, Christof}, title = {Modelling opinion dynamics under the impact of influencer and media strategies}, volume = {13}, journal = {Scientific Reports}, arxiv = {http://arxiv.org/abs/2301.13661}, doi = {10.1038/s41598-023-46187-9}, pages = {19375}, year = {2023}, abstract = {Digital communication has made the public discourse considerably more complex, and new actors and strategies have emerged as a result of this seismic shift. Aside from the often-studied interactions among individuals during opinion formation, which have been facilitated on a large scale by social media platforms, the changing role of traditional media and the emerging role of "influencers" are not well understood, and the implications of their engagement strategies arising from the incentive structure of the attention economy even less so. Here we propose a novel opinion dynamics model that accounts for these different roles, namely that media and influencers change their own positions on slower time scales than individuals, while influencers dynamically gain and lose followers. Numerical simulations show the importance of their relative influence in creating qualitatively different opinion formation dynamics: with influencers, fragmented but short-lived clusters emerge, which are then counteracted by more stable media positions. Mean-field approximations by partial differential equations reproduce this dynamic. Based on the mean-field model, we study how strategies of influencers to gain more followers can influence the overall opinion distribution. We show that moving towards extreme positions can be a beneficial strategy for influencers to gain followers. Finally, we demonstrate that optimal control strategies allow other influencers or media to counteract such attempts and prevent further fragmentation of the opinion landscape. Our modelling framework contributes to better understanding the different roles and strategies in the increasingly complex information ecosystem and their impact on public opinion formation.}, language = {en} } @article{WolfFuerstGeigesetal.2023, author = {Wolf, Sarah and F{\"u}rst, Steffen and Geiges, Andreas and Laublichler, Manfred and Mielke, Jahel and Steudle, Gesine and Winter, Konstantin and Jaeger, Carlo}, title = {The Decision Theatre Triangle for societal challenges - an example case and research needs}, volume = {394}, journal = {Journal of Cleaner Production}, doi = {10.1016/j.jclepro.2023.136299}, pages = {136299}, year = {2023}, abstract = {Tackling societal challenges relating to sustainability requires both an understanding of the underlying complex socio-ecological systems and participation of scientists as well as relevant stakeholders, such as practice experts, decision makers, and citizens. This paper introduces the Decision Theatre Triangle, a method which combines empirical information, mathematical modelling and simulation, and a format for dialogue between scientists and stakeholders. While it builds on previous Decision Theatre work, the new structuring into these three elements emphasizes what is needed for setting up a Decision Theatre for a given challenge. Based on experience with a specific example - sustainable mobility in Germany - it is argued that agent-based models are particularly suitable for Decision Theatres and that the method is useful not only for decision support but also for science communication and co-creation of a deeper knowledge of the system under discussion. As a step towards facilitating a broader use of the Decision Theatre Triangle method, the paper then sketches research needs for each of its three elements, with a focus on mathematical modelling and simulation.}, language = {en} } @article{FischerHolzhausenRoeblitz2022, author = {Fischer-Holzhausen, Sophie and R{\"o}blitz, Susanna}, title = {Hormonal regulation of ovarian follicle growth in humans: Model-based exploration of cycle variability and parameter sensitivities}, journal = {Journal of Theoretical Biology}, doi = {https://doi.org/10.1016/j.jtbi.2022.111150}, year = {2022}, abstract = {We present a modelling and simulation framework for the dynamics of ovarian follicles and key hormones along the hypothalamic-pituitary-gonadal axis throughout consecutive human menstrual cycles. All simulation results (hormone concentrations and ovarian follicle sizes) are in biological units and can easily be compared to clinical data. The model takes into account variability in follicles' response to stimulating hormones, which introduces variability between cycles. The growth of ovarian follicles in waves is an emergent property in our model simulations and further supports the hypothesis that follicular waves are also present in humans. We use Approximate Bayesian Computation and cluster analysis to construct a population of virtual subjects and to study parameter distributions and sensitivities. The model can be used to compare and optimize treatment protocols for ovarian hyperstimulation, thus potentially forming the integral part of a clinical decision support system in reproductive endocrinology.}, language = {en} } @article{FischerHolzhausenRoeblitz2022, author = {Fischer-Holzhausen, Sophie and R{\"o}blitz, Susanna}, title = {Mathematical modelling of follicular growth and ovarian stimulation}, journal = {Current Opinion in Endocrine and Metabolic Research}, doi = {https://doi.org/10.1016/j.coemr.2022.100385}, year = {2022}, language = {en} }